The team @ Skilldrive http://www.skilldrive.com have put together a really interesting presentation which is targetted at developers but I think it works well for IT Professionals too. If you'd like to understand how the logon process works, how Windows handles encryption and authentication & storing secrets then it's worth a look.

The content includes over one hundred technical slides and the agenda's described as follows: 

"Security IDentifier, Logon Session, ACL, Privileges, LSA
Authentication protocols
Impersonation
Encryption, CryptoAPI
Data Protection API
Code based security
Role based security
Auditing"

You can download the slides for free from http://www.skilldrive.com/WindowsSecIntEngOut.zip